The risk of major structural birth defects associated with seasonal influenza vaccination during pregnancy: A population‐based cohort study

Abstract

Introduction Seasonal inactivated influenza vaccine (IIV) is routinely recommended during pregnancy to protect both mothers and infants from complications following influenza infection. While previous studies have evaluated the risk of major structural birth defects in infants associated with prenatal administration of monovalent pandemic IIV, fewer studies have evaluated the risk associated with prenatal seasonal IIV. Methods We conducted a population‐based cohort study of 125,866 singleton births between 2012 and 2016 in Western Australia. Birth registrations were linked to the state's registers for congenital anomalies and a state prenatal vaccination database. We estimated prevalence ratios (PR) of any major structural birth defect and defects by organ system. Vaccinated pregnancies were defined as those with a record of IIV in the first trimester. Inverse probability treatment weighting factored for baseline probability for vaccination. A Bonferroni correction was applied to account for multiple comparisons. Results About 3.9% of births had a major structural birth defect. Seasonal IIV exposure during the first trimester was not associated with diagnosis of any major structural birth defect diagnosed within 1 month of birth (PR 0.98, 95% CI: 0.77, 1.28) or within 6 years of life (PR 1.02, 95% CI: 0.78, 1.35). We identified no increased risk in specific birth defects associated with seasonal IIV. Conclusion Based on registry data for up to 6 years of follow‐up, results suggest there is no association between maternal influenza vaccination and risk of major structural birth defects. These results support the safety of seasonal IIV administration during pregnancy.

A Prospective Cohort Study on Pregnancy Outcomes of Persons Immunized with a Seasonal Quadrivalent Inactivated Influenza Vaccine during Pregnancy

“…Our findings are consistent with previous studies looking at all influenza vaccines combined (i.e., irrespective of type and brand), showing that maternal immunization does not increase the risk of adverse pregnancy outcomes [ 7 , 11 , 12 , 13 , 14 , 15 , 23 ]. In this study of 483 pregnant persons vaccinated with IIV4 between 2017 and 2021, the live birth rate was >98%, and adverse maternal and infant outcomes were comparable to—or even lower than—national averages.…”

Vaccination during pregnancy: A golden opportunity to embrace

“…1 The influenza vaccine reduces the risk of complications for the mother, but also has substantive benefit for the infant, with no risk related to major structural birth defects, and can be given in any trimester of pregnancy. 7 The Tdap vaccine is recommended for preventing pertussis infection in the newborn, so it is routinely delivered in the late second or early third trimester to maximize antibody transfer to the infant at the time of delivery. 8 With administration in the third trimester, antibodies transmitted to the fetus showed an efficacy of 77.7% against the disease for newborns, and a protection of 90.5% against severe cases.…”

Cohort profile: A population-based record linkage platform to address critical epidemiological evidence gaps in respiratory syncytial virus and other respiratory infections

“…While our current focus is on RSV and the platform was built with RSV in mind, the Respiratory Infections Linked Data Platform will provide a valuable resource for wider epidemiological research on other respiratory viruses and infections in the future. Members of our team have longstanding expertise using linked population data in previous analyses, including the evaluation of maternal influenza and pertussis vaccine safety and effectiveness [18,19], and direct and indirect effects of maternal [20][21][22] and childhood [16,23] vaccines, which has aided the design of this platform and will assist with investigations of all respiratory infections. The Respiratory Infections data platform will enable evaluation of the direct and indirect effects of maternal RSV vaccines and/or monoclonal antibodies on RSV and non-RSV hospitalisations.…”